Add new RPC method to get the chain type (#5576)

* Add new RPC method to get the chain type

This adds a new RPC method to get the chain type of the running chain.
The chain type needs to be specified in the chain spec. This should make
it easier for tools/UI to display extra information without needing to
rely on parsing the chain name.

* Update client/rpc-api/src/system/mod.rs

Co-Authored-By: Tomasz Drwięga <tomusdrw@users.noreply.github.com>

* Primitive crate

* Feedback

Co-authored-by: Tomasz Drwięga <tomusdrw@users.noreply.github.com>

substrate/primitives/chain-spec/Cargo.toml

@@ -0,0 +1,13 @@
+[package]
+name = "sp-chain-spec"
+version = "2.0.0-alpha.5"
+authors = ["Parity Technologies <admin@parity.io>"]
+edition = "2018"
+license = "GPL-3.0"
+homepage = "https://substrate.dev"
+repository = "https://github.com/paritytech/substrate/"
+description = "Substrate chain configurations types."
+
+[dependencies]
+serde = { version = "1.0.101", features = ["derive"] }
+serde_json = "1.0.41"